Abstract
Under droplet impingement, surface leading edge protection (LEP) coating materials for wind turbine blades develop high-rate transient pressure build-up and a subsequent relaxation in a range of strain rates. The stress-strain coating LEP behavior at a working frequency range depends on the specific LEP and on the material and operational conditions, as described in this research in a previous work. Wear fatigue failure analysis, based on the Springer model, requires coating and substrate speed of sound measurements as constant input material parameters. It considers a linear elastic response of the polymer subjected to drop impact loads, but does not account for the frequency dependent viscoelastic effects for the materials involved. The model has been widely used and validated in the literature for different liquid impact erosion problems. In this work, it is shown the appropriate definition of the viscoelastic materials properties with ultrasonic techniques. It is broadly used for developing precise measurements of the speed of sound in thin coatings and laminates. It also allows accurately evaluating elastic moduli and assessing mechanical properties at the high frequencies of interest. In the current work, an investigation into various LEP coating application cases have been undertaken and related with the rain erosion durability factors due to suitable material impedance definition. The proposed numerical procedures to predict wear surface erosion have been evaluated in comparison with the rain erosion testing, in order to identify suitable coating and composite substrate combinations. LEP erosion performance at rain erosion testing (RET) technique is used widely in the wind industry as the key metric, in an effort to assess the response of the varying material and operational parameters involved.
Highlights
Wind power has become a key technology to provide electricity from renewable and low-emission sources [1]
It is important to note that polymeric materials recently applied on the leading edge protection (LEP) systems are mainly viscoelastic materials with good properties for impact energy attenuation in erosion applications [16], that develop different mechanical response depending on temperature and on stress and strain rates [17,18,19]
The analysis considers rain erosion testing (RET) testing results obtained at ORE-Catapult [41] with a configuration of coating LEP19B layer with a Primer layer and the laminate
Summary
Wind power has become a key technology to provide electricity from renewable and low-emission sources [1]. It is important to note that polymeric materials recently applied on the LEP systems are mainly viscoelastic materials with good properties for impact energy attenuation in erosion applications [16], that develop different mechanical response depending on temperature and on stress and strain rates [17,18,19]. If these parameters are not incorporated in the mechanical modeling, the predicted stresses of the coating behavior under impingement may wrongly consider the material capabilities. LEP erosion performance at rain erosion accelerated testing technique is used as the key metric in an effort to assess the response of changing material and processing parameters involved and to evaluate the lifetime accuracy analysis
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